Echoing Fury

It has a high chance to Fear on hit, and before patch 2.0., due to damage allocation bug, offered the highest plain base damage in game. An Echoing Fury with socket and Life Steal would have been the most expensive one-handed weapon on the Auction House.

As of patch 2.6.6, it gained a unique affix, an opposite of Stone Gauntlets: each enemy killed adds a stacking (up to 5 times) boost to attack speed and movement speed, up to 75% / 25% total. This works on kill assists and pet kills.